Marc Kleine-Budde
b46d8c1c70
All devices behind a SPI controller have the same udev ID_PATH property. This is a problem for predicable network names for CAN controllers. CAN controllers, in contrast to Ethernet controllers, don't have a MAC Address, so there's no way to tell two CAN controllers on the same SPI host controller apart: $ udevadm info /sys/class/net/can0 P: /devices/platform/soc/fe204000.spi/spi_master/spi0/spi0.1/net/can0 L: 0 E: DEVPATH=/devices/platform/soc/fe204000.spi/spi_master/spi0/spi0.1/net/can0 E: INTERFACE=can0 E: IFINDEX=3 E: SUBSYSTEM=net E: USEC_INITIALIZED=11187199 E: ID_PATH=platform-fe204000.spi E: ID_PATH_TAG=platform-fe204000_spi E: SYSTEMD_ALIAS=/sys/subsystem/net/devices/can0 E: TAGS=:systemd: $ udevadm info /sys/class/net/can1 P: /devices/platform/soc/fe204000.spi/spi_master/spi0/spi0.0/net/can1 L: 0 E: DEVPATH=/devices/platform/soc/fe204000.spi/spi_master/spi0/spi0.0/net/can1 E: INTERFACE=can1 E: IFINDEX=4 E: SUBSYSTEM=net E: USEC_INITIALIZED=11192211 E: ID_PATH=platform-fe204000.spi E: ID_PATH_TAG=platform-fe204000_spi E: SYSTEMD_ALIAS=/sys/subsystem/net/devices/can1 E: TAGS=:systemd: With this the chip select number is added to the ID_PATH, to make predictable network names possible. $ sudo udevadm info /sys/class/net/can0 P: /devices/platform/soc/fe204000.spi/spi_master/spi0/spi0.1/net/can0 L: 0 E: DEVPATH=/devices/platform/soc/fe204000.spi/spi_master/spi0/spi0.1/net/can0 E: INTERFACE=can0 E: IFINDEX=3 E: SUBSYSTEM=net E: USEC_INITIALIZED=11187199 E: ID_PATH=platform-fe204000.spi-cs-1 E: ID_PATH_TAG=platform-fe204000_spi-cs-1 E: SYSTEMD_ALIAS=/sys/subsystem/net/devices/can0 E: TAGS=:systemd: $ sudo udevadm info /sys/class/net/can1 P: /devices/platform/soc/fe204000.spi/spi_master/spi0/spi0.0/net/can1 L: 0 E: DEVPATH=/devices/platform/soc/fe204000.spi/spi_master/spi0/spi0.0/net/can1 E: INTERFACE=can1 E: IFINDEX=4 E: SUBSYSTEM=net E: USEC_INITIALIZED=11192211 E: ID_PATH=platform-fe204000.spi-cs-0 E: ID_PATH_TAG=platform-fe204000_spi-cs-0 E: SYSTEMD_ALIAS=/sys/subsystem/net/devices/can1 E: TAGS=:systemd:
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